Vacuum tube



Sept. 19, 1933. P. E. EDELMAN VACUUM TUBE Filed Aug. 25, 1925 PM/e .ff/Mm y MW- ys. I

Patented Sept. 19, 1933 1,927,631 vVACUUM TUBE Philip E. Edelman,

Chicago, Ill.

New York, N; Y., assignor, by mesne assignments, to Robert'T. Mack,

trustee,

YApplication August 25, 1923. serial No. 659,263

1s claims.y (01.250-215) An object of the present invention is to provide an economical simplified apparatus which is sensitive and stable in operation, faithful in reproduction, and satisfactory in volume.-

A further Objectis toxprovide vacuum tube apparatus in which the heating element or filament may be easily renewed, thus greatly increasing the useful life of such tubes. i

These objects and others will presently appear' as reference is made to the accompanying drawing in which Figure 1 is a schematic diagram, by way of example, of a suitable radio vacuum tube, embodying my invention. l

My invention relates more particularly to the improvedjvacruum tube construction herein set forth whereby a good tight seal is obtained inl the tube per se, permitting the heater for` the cathode to be renewed without breaking said seal. The vacuum tube improvement set-forth can be used in any standard type of radio receiver' or circuit, operated from'any suitablevsource of current. It comprises a glass or quartz container 11 having an indented portion 14`within which the heating element 15 may be inserted or withdrawn without 'disturbing the vacuum -in tube 11.- Tube 11 has seals 10 supporting respectively the plate or anode' 13, the grid or control electrode 12, and ,the wire 9 which connects with the electron emit ting surface 8.V The electron emitting surface 8 may be constructed by depositing a platinized, lm coating 22 on the indented portion 14 of tube 11. On this platinized film 22 to whichl wire 9 is electrically connected, are placed coatings of `electron emitting mixed metallic oxides, such as calcium, bismuth, and strontium oxides. Y Any vother suitable electron emitting surfacermay be connected to the wire9. The heating element 15 transfers heat to the electron emitting surface 8 by conduction and radiation through the thin portion' 14 of tube 11. This heater 15 can be con structed in any s table manner, preferably from fine nichrome or other heating wire material which does not readily oxidize. The heater 15 is supported by wires 16 in a remov ble insulating plug 17 which lits on 'tube' 11. When the heater or filament 15 burns out the plug 17 can be removed Without disturbing' the tube 11 or its connections and without breaking its vacuum, so that a .plug 17 with a relled heater 15 can be inserted back in place,` as shown. This affords a tube having good operating characteristicswith economy in operation.

It maybe remarked that'the heater element 15- preferably comprises a re-entrant looped wire 15,l as shown in theV ligure, which is normally substantially spaced from land not disposed against insulator 14. YThe electromagnetic field ofv force normally set upV by passage-ofelectric current through one leg of U-shaped heater filament 15 thereby tends to oppose that set up vby the reother leg thereof` .andato minimize undesired electromagnetic force action..

f l Also as heater element 15 is-heated it naturally tends to expand and my preferred construction as shown,prevents cracking of or damage to iin-K` turnv passage ofv the same current through the .3 Y Y sulator 14 by providing the small clearance space shown' between, elements 15 and 14; permitting element l5 to move with respect to element 14-as element 15 is heated.

Further it will be observed that electrically oonductive surface 22 on yinsulator 14 extends substantially overa greater portion ofinsulator 14 than heater'element 15 extends into. Thereby-the electrostatic field of force set uprby application of electricityto member 15`issubstantially shielded by conductive coating 22. lTofurther afford this desired result, asshown, `itwill be observed that the electron emitting surface 8, preferablyA does` not cover the entirensurface4 of conductive coating 22so thatelectrons `,maybejemitted from surface 22 substantially free from undesired interfering electrostatic 'forces set upby normal' flow of electricityr through'heater Wire 15. v

It is an important advance in this; art to,` have the cathode .conductive-surface` 14 cover more area of insulator 14than is employed te support electron emitting surface 8 via said conductive surface 22. Also it is an advance in this-art to .have heater- Wire-'15 and electron emitter surface 8 so relatively disposed with respect to electrically conductive coating 22 that surface 22 not only extends between elements Vl5 and `8 vbut also projects beyond the relatively adiacently disposed members' 15 and 8. Also itis anim.- Y

portant advance in this art to have member l5 relatively `loosely mounted Withrespect to insulator 14 so as to have substantially a free closely spaced relation with respect thereto.

It will also be Vevidentthaty members 15, 14, 22

.and 8 are preferably so relatively mounted with respect to grid 12 andplate 13, as shown; that the electron stream set up by emitting surface -8 strikes members 12 and 13 substantially free from the influence of elds of force normally set up by the ow 'of electricity through heater wire 15. Thereby means are afforded to'preventi grid 12 from being electrically 'detrimentally influenced by fields of force extending `from heater' element 15. Y

ous changes may be made without departing from` Y ythe spirit of my invention and of the appended claims.

I claim:

1. Ina radio vacuum tube, a glass bulb having a hollow re-entrant cathode holder projecting inwithin the scope wardly therein, and closedatits end to formv with the bulb a continuous envelope, a cathode supported on said holder, a heater element renewably held within said holder adjacent to said cathode, and cooperating grid and plate electrodes sealed in said bulb, said bulb being evacuated and said vacuum vmaintained bythe continuous surface `of lsaidY glass bulb. Y v

2. In a threeelementvacuumtube having a sealingbulb, the improvement which comprises a divided structure for the cathode element thereof,

consisting of an electron emitting part and a thermal element Vfor actuating said electron emitting part, and an insulating tube formedias a part of'said sealing bulbV and extending between said electron emitting part and said thermal element, and a connector support for said thermal element to hold the same in operative position with respectto said sealing bulb and said insulating tube. Y

3. In an audion having an envelope, a cathode,-

and grid and plate electrodes therefor, a structure for said cathode comprising a hollow insulating member, a heater element `disposed in and spaced from said insulating member, an elecltrical conductive coating externally carried by said insulating member, and a surface coating on said conductive member capable of emitting electrons when saidconductive member is heated.

4. In an audion having an envelope, a cathode, and co-operating electrodes therefor, a structure for said cathode comprising Ya hollow insulating membena U-shaped heater element disposed in vand spaced from saidV insulating member, an

electrical conductive'coating externally carried by said insulating member, and a surface coating on said conductive member capableof emit- Vting electrons when said conductivev member is heated. I f

5. Ina vacuum tube having an envelope, a

cathode, and co-operating electrodes therefor,

said cathode comprising an insulator member, an electrical conductor coated on 'said insulator member, a coating capable of emitting electrons contacting with said electrical conductor', and an electrical heater-element disposed to heat said `insulator member, said electrical conductor not only extending between but also projecting beyond said heater-element and said coating.

6. In a vacuum tube having an envelope, a cathode, and co-operating electrodes therefor, said cathode comprising an insulator member, an electrical conductor `coated on said insulator member, an oxide coating capable of emitting electrons Acovering a substantial portion but not all of saidA electrical conductor, and an electrical -heater element-disposed withinA said insulator member to heat same, the portion of said electrical conductor not so coated by said electron emitting coating projecting beyond the heater element.

f '1. In an audion having an envelope, a cathode,

and co-operating electrodes therefor, a structure for said cathode comprising a hollow insulating member, a heater elementl disposed in and spaced from said insulating member, anelectrcal conductive coating externally carriedY by said insulating member, and a surface coating on said conductive member capablel of emitting electrons when said conductive member is heated.

8. In a thermionic device, an evacuated container having a re-entrant portion of insulating material, acathode within the container and in engagement with the re-entrant part of the wall thereof, a heating device external to said con- .tainer and within/the recess formed by said reentrant portion and means for retarding ilow of heatfrom said, recess to the external air.

"9. An kequipote`ntial-vacuum tube having a vitreous envelope which is coated on its inner surface with an electron-emitting material to constitute a cathode,` and means' outside of the envelope for-rendering the material'thermionically active. 5 i 1.0. A cathodestructure conriprisingA a single hollow member adapted Vto emit electrons when heated, a heating 'member within said-emitter and a plug engaging an end of said emitter and `having an enlarged portion extendingoutwardly beyond the end thereof, formmaintaining-said heating member in spaced relation `to said emitting member.v l Y 11. In a vacuum tube having anY envelope, a cathode, and co-operating electrodes therefor, said cathode comprisingan insulator member,

an electrical conductor carried on said insulator member, a coating capable of emitting electrons contacting with said electrical conductor, and an electrical heater element disposed to heat said insulator member, said electrical conductor not only extending betweenbut also projecting vbeyond said heater element and said coating.

y12. In a vacuum' tube having an envelope, a cathode, and co-operating electrodes therefor, said cathode comprising an insulator member, an

electrical conductor carried on said insulator.

member, an oxide coating4 Vcapable of emitting electrons covering a substantial yportion but not all of said electrical conductor, and an electrical heater element disposed within said insulator member to heatsame, the portion of `said electrical conductor not so coated by said electron emitting coating projecting beyond the said ad jacently disposed heater element.

13. In a thermionie device, a cylindrical cathode, a vheating vdevice therefor, and an evacuated envelope electrically separating the heating device from the cathode, the heating device being external to said envelope and heating the cathode by heat radiation through'the envelope from the heating device, whereby readily replaceable. l

- 14. In a thermionic device, a cylindrical cathode, a heater element therefor, and an` evacuated envelope electrically separating the heater element from the cathode, the heater element being external to said envelope and heating the cathode by heat radiationV through the 'envelope from the heater element, said heater element being adaptedto be heated by the passage of an'electric current therethrough, whereby the heater element is readily replaceable.

15. In a thermionic vacuum tube, a `cathode structure comprising a electrode, Van electron emitting yelement thereon, an insulator supporting said electrode, and a heater filament dis-v posed in said insulator, said electrodel extending the heating rdevice is` as a shield between said filament and said electron emitting element and projecting beyond the electron emitting element. Y y 1 16. In a vacuum tube having a cathode, a structure for said cathode which comprises a hollow electrical insulator capable of transferring heat, a U-shaped heater filament expansibly disposed therein so that said filament may freely expand when heated with respect to said insulator, an electrode carried by saidinsulator and insulated thereby from said filament, and an electron emitting coating on said electrode.

17. In a thermionic tube having a cathode, a. structure for said cathode which comprises an electrical insulator capable of transferring heat, a U-shaped heater filament expansibly disposed therein so that said filament may freely expand Whenheatedwth respectto said insulator, an electrode disposedabout said insulator and insulated thereby from said filament, and an electron emitting coating on said electrode. t y

18. In a thermionic tube lhaving a cathode, a structure for said cathode which comprises an electrical insulator capable of transferring heat,

la U-shaped heater filament expansibly disposed therein so that said filament may freely expand when heated with respect toy said insulator, an-

electrode disposed about said insulator and insulated thereby from said filament,V and an electron emitting coating on said electrode, the `electrode projecting beyond the electron emitting coating so as to form a shield therefor.

PHILIP E. EDELMAN. 

